Abstract: Temporal issues of importance include timing, magnitude, and return frequency of flow conditions as well as duration of exposure (concentration) and return frequency of specific exposure levels. Urbanization alters flow regime and produces unit-hydrograph changes. Water quality is also altered by urban runoff, stream conditions may be dependent on both control technologies used and landuse activities present in the watershed. Spatial issues are important because biological conditions will vary with location in the watershed. This paper views the streams receiving urban runoff in the context of the total watershed. Streams should not be viewed as conduits for the transfer of runoff. Suggested mitigation and control procedures incorporate both temporal and spatial dynamic aspects of the watershed.